The inexplicable brown discharge in the fifth month of pregnancy may be caused by preeclampsia, gynecological diseases, placenta hypoplasia and so on. 1. Pre-eclampsia: When pre-eclampsia occurs, there may be brown discharge, but at the same time may also be accompanied by abdominal distension, swelling and other discomfort. 2. Gynecological diseases: When cervical polyps, vaginitis, cervicitis, pelvic inflammatory disease, adnexitis and other gynecological diseases are not treated in time, abnormal discharge may also occur. 3. Placenta hypoplasia: If the placenta is too close to the endocervical opening, or even covering the endocervical opening, it may also cause bleeding, and when the bleeding is relatively small and the vaginal secretions are mixed and discharged later, it is mostly manifested as a brown discharge. The 5 months of pregnancy inexplicable brown discharge belongs to the abnormal phenomenon, it is recommended to go to the hospital in a timely manner, in the doctor’s interview combined with the relevant project examination, to clarify the specific causes of the targeted treatment.